Evaluate the following expression when $c = 3$ and $d = 1$. $7$ $c$ $ + 7$ $d$ $ - 4$
Solution: Substitute $3$ for ${c}$ and $1$ for ${d}$ $ = 7{(3)} + 7{(1)} - 4 $ $ = 21 + 7 - 4 $ $ = 24$